As one of the manufacturing methods for single crystal silicon, the CZ method is available.
The single crystal silicon (ingot) which is grown and pulled up by the CZ method is sliced, polished, and etched to be provided as a silicon wafer for manufacturing semiconductor devices.
More specifically, an impurity, such as boron B or the like, is added into melt in order to provide a desired resistivity for the silicon wafer before the single crystal silicon is pulled up from the melt.
Herein, in the process of pulling-up the single crystal silicon for growing it, the impurity is not uniformly incorporated. Therefore, when a silicon wafer acquired from the single crystal silicon (ingot) which has been pulled up for growing is cut in the longitudinal direction (perpendicularly with respect to the wafer surface), striations according to a variation in concentration of the impurity are observed. And across the wafer surface, the variation in impurity concentration is observed as ring-shaped figures.
On the other hand, in recent years, a high-level specification for planarity of the silicon wafer is required for some types of semiconductor devices.
As a related art in connection with the present invention, the following patent literature 1 is available.
This patent literature 1 discloses the invention in which the variation in oxygen concentration appearing across the silicon wafer surface is reduced, paying attention to the oxygen incorporated from the quartz crucible into the single crystal silicon through the melt. The technique used in the patent literature is to reduce the variation in oxygen concentration across the silicon wafer surface by setting the ration h/d between the overlap length h of the slit of the heater and the inner diameter d of the heater to 0.70 or under.    Patent literature 1: Japanese Patent Application Laid-Open No. 11-116390